The present invention relates to an oil seal arrangement for the shaft of a turbocharger.
In FIG. 1 is shown a prior art turbocharger. The lubricant is forcibly charged through an oil port e so as to lubricate a floating metal b, a thrust bushing c and a thrust metal d which support a turbine shaft a rotating at a high speed. The pressure at the rear of a blower impeller f becomes negative depending on its rotational speed and operating conditions. As a result, the lubricant is sucked into the blower through very small spaces between the component parts so that it is entrained as oil mist in the air discharged from the blower. The oil mist adversely affects the performance and maintenance of the turbocharger and its associated engine.
In order to overcome this problem, the prior art turbocharger is provided with an oil thrower g, a seal ring j interposed between the oil thrower g and a seal plate h on the side of the bearing and another seal rink k interposed between the oil thrower g and a seal plate i on the side of the impeller, thereby preventing the leakage of the lubricant into the blower. More specifically, the lubricant is first thrown under the centrifugal force of the oil thrower g and the remaining oil which has not been thrown is sealed by the seal rings j and k. The lubricant which has been thrown and sealed in the manner described above is directed toward an outlet l along the surfaces of the seal plates i and h.
The pattern of the thrown oil changes over a wide range depending upon the rotational speed of the turbine shaft and the flow rate of the lubricant forced to flow through the oil inlet e. That is, the thrown oil is in the form of drops, film, sawteeth, mist containing air bubbles and combinations thereof. The thrown oil impinges against the surfaces of the component parts and drops along them. Sometimes the flow of the oil is prevented by the oil films formed on the surfaces of the component parts. Thus the lubricant is discharged to the exterior without leaking into the blower. However, it occurs very frequently in practice that the discharged lubricant is sucked into the blower because of careless handling. Therefore the complete prevention of the lubricant leakage into the blower cannot be attained by the prior art oil seal system. In addition, the prior art system cannot seal the oil whose conditions change in various manners.
It is therefore the primary object of the present invention to provide an oil seal system for the shaft of a turbocharger which can accomplish the complete oil throwing so as to prevent any leakage of the lubricant to a blower.
The present invention will become apparent from the following description of a preferred embodiment thereof taken in conjunction with the accompanying drawings.